Bigeminal rhythm due to reentrant ventricular extrasystoles coupled to ventricular and A-V junctional escapes: comparison with ventricular parasystole associated with ventricular extrasystoles of bundle branch reentry.

Bigeminal rhythm due to reentrant ventricular extrasystoles coupled to either ventricular escape of varying aberrant conduction or atrio-ventricular (A-V) junctional escape in association with coexisting idioventricular rhythm and A-V junctional rhythm is presented (Case 1). Dual A-V pathways with longitudinal dissociation in the left bundle branch was presumed to be the mechanism. Generally, both ventricular and A-V junctional escapes were discharged and reset as a result of the retrograde concealed conduction of the reentrant ventricular extrasystoles and the arrhythmia was thought to represent a variant of parasystole. Ventricular parasystole associated with ventricular bigeminy of bundle branch reentry, which was precipitated by hypokalemia during administration of a thiazide diuretic, was added for comparison (Case 2). In the latter, a reentrant ventricular extrasystole arising from the left anterior fascicle brought on and terminated ventricular parasystolic trigeminy and hexageminy of left posterior fascicular origin. Longitudinal dissociation with unidirectional block in the left posterior fascicle was presumed to be the mechanism. At times intermittent ventricular extrasystoles with broad and notched QRS in leads II and III initiated recurrent runs of ventricular bigeminy of varying bundle branch reentry.